/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:
    bool isLeaf(TreeNode* root) {
        return (root -> left == NULL) && (root->right == NULL);
    }

    bool hasPathSum(TreeNode* root, int sum) {
        if (root == NULL)
            return false;
        sum -= root->val;
        if (isLeaf(root) && sum == 0)
            return true;
        return hasPathSum(root->left, sum) || hasPathSum(root->right, sum);
    }
};
